Process and apparatus for the production of calcium carbide



PROCESS AND APPARATUS FOR THE PRODUCTION OF CALCIUM CARBIDE Filed Aug.16, 1955 2 Sheets-Sheet 1 s. KGOPAL ET AL PROCESS AND APPARATUS FOR THEPRODUCTION OF CALCIUM CARBIDE Filed Aug. 16, 1955 Oct. 28, 1958 2Sheets-Sheet 2 FIG. 2

United States Patent Ofidce 2,858,197 Patented Oct. 28, 1958 PROCESS ANDAPPARATUS FOR THE PRODUC- TION OF CALCIUM CARBIDE Sleds Koopal, Sittard,and Willem van Loon, Geleen, Netherlands, assignors to Stamicarbon N.V., Heerlen, Netherlands Application August 16, 1955, Serial No. 528,578Claims priority, application Netherlands August 18, 1954 7 Claims. (Cl.23--277) The present invention is directed to a process and apparatusfor the production of calcium carbide and a combustible gas, by feedinginto a furnace a solid carbonaceous fuel, e. g., coke, coal or othersolid fuel with high carbon content and limestone, dolomite, burnt lime,or other sources of calcium oxide (hereinafter referred to by thegeneric term lime). The temperature and energy needed for thecarbide-forming reaction are obtained by burning part of the fuel with ablast enriched in oxygen, blown into the fuel bed through a ring oftuyeres, the remaining fuel being used to react with the lime, so thatcalcium carbide is formed. The carbide is drawn off in the molten statefrom the bottom of the reactor.

Hitherto, it has been common practice to supply both the fuel and lime,either mixed or unmixed, at the top of the furnace, the charge sinkingtowards the hearth of the furnace in countercurrent relation to the hotcombustion gases. A disadvantage of this way of operating the process isthat the very hot, rising combustion gases cause considerablevaporization of lime components. These components sublime at colderplaces higher up in the bed and create many difiiculties due to blockingand bridging of the charge.

It is an object of the present invention to develop a method andapparatus for preparing calcium carbide from a solid carbonaceous fueland source of calcium oxide, as previously set forth, while obviatingthe vaporization of lime components with the attendant blocking andbridging of the charge.

It is another object of the invention to devise such a method andapparatus that the calcium oxide containing material and the carbideformed therefrom does not come into contact with the hot gas currentproduced in the combustion of the solid carbonaceous fuel with theoxygen-rich blast.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

It has now been found that, in contrast with the method of operation ofthe prior art process, set forth above and previously consideredessential for successful production of calcium carbide, the carbide canbe successfully produced, if the calcium oxide-containing material isfed into the reaction zone in such a way that said material, as well asthe carbide formed therefrom, cannot come into contact with the hot gascurrent produced in the combustion of the solid fuel with theoxygen-rich blast.

In carrying out the method of operation according to the invention, aminor amount of carbonaceous material, e. g., 0% up to 10% of the totalamount of carbonaceous material, preferably is mixed and burned with theincoming lime charge for the purpose of preheating the charge in anamount of 0 parts of lime by weight. In actual practice of the presentinvention, the difiiculties mentioned above in connection with the priorart procedure were completely solved and it was found that, bycombustion of the fuel in the hearth zone, sufficient heat was radiatedto the zone of carbide formation to effect a rapid and nearlyquantitative conversion of the lime into calcium carbide.

It is known that, for the carbide-forming reaction to occur,considerably higher temperatures are required than for the preparationof combustible gases by counter-current gasification of solid fuels withoxygen and steam or carbon dioxide or oxygen with both steam and carbondioxide. Thus, for the carbide forming reaction, temperatures of 2400 C.to 3000 C. are employed, while in preparing the combustible gases,temperatures of 1600 C. to 2000 C. are required. Nevertheless, with themethod according to the present invention, sufficient heat is left inthe gases which rise from the fuel bed to supply sufficient calories forutilization by blowing steam or carbon dioxide, or a mixture of thesegases, over the hearths into the generators, in order to convert thissteam with part of the coke or other carbonaceous fuel supplied intocarbon monoxide and hydrogen or to convert the carbon dioxide to carbonmonoxide.

Illustrative ways of carrying out the invention will now be describedwith reference to the accompanying drawing, in which Figure 1 shows inlongitudinal section partly diagrammatically a suitable furnace, inwhich the method according to the invention can be carried out; and

Figure 2 shows a similar furnace with modified means for introducing thelime charge.

Referring to Figure 1, a furnace chamber 1 is provided at its top with afilling lock It: for the supply of the carbonaceous fuel, e. g., coke orcoal, and at the bottom with an underfeed device 2 for the supply oflime. The furnace chamber is furthermore provided with a ring of tuyeresor burners 3 for the supply of the oxygencontaining blast, a ring ofblast openings 4 at some dis tance over these burners for the supply ofan endothermic gasification agent, e. g., steam or carbon dioxide, adischarge opening 5 for the gas produced and a tap hole 6 for theremoval of the carbide produced.

The underfeed device 2 is fed via a conduit 8 from a bunker 8a, filledwith lime, while the discharge from the device 2 into the furnacechamber takes place through conduit 7, which may, if desired, beequipped with feed pipes fa for air or oxygen for burning a minor amountof carbonaceous material to preheat the lime charge.

Q-enerady (with either the furnace of Figure 1 or that of Figure 2), forevery 1000 kg. of calcium oxide fed into the furnace chamber 1 throughunderfeed device 2, there are ted 3800 to 4800 kg. of coke throughfilling lock in; 2000 to 3000 kiloliters (standard temperature andpressure) of oxygen from the tuyeres 3, 500 to 900 ltiloliters of steamor carbon dioxide (standard temperature and pressure) from blastopenings t and, preferably, 0 to 350 kiloliters (standard temperatureand pressure) of oxygen through feed pipes 7n. As previously indicated,there can be mixed with the lime charge, e. g., in bunker 8a, 0 to 400kg. of carbonaceous fuel, e. g., coke, per 1000 kg. of lime.

The underfeed mechanism proper of Figure 1 consists of a hydraulic ram9, connected to a plunger 10 guided in a cylinder 11. The cylinderpivots about a horiis attached to the upper end of the cylinder.

parts up to 40 parts per 3,, ns Q a hydraulically driven plunger 14, thecylinder can be reciprocated in such a way, that in the one'position itsupper end connects to the conduit 8, the plunger then being in itslowermost position, and the conduit 7 being closed; by the slide. al ve13, In this position, the cylinder 11 may be filled with the lime ar eii st uemla hem-singe 1.0. e ur e t h position illustratedfso thatconduit #1 is closed by slide valve 13 and cylinder. ll'co 'in ects toconduit 7, so that the plunger may. push the lime. content of the saidcylinder into the, conduit 7,

The apparatus according to Figure 2 comprises a furnace of lthesametypeas shown. in Figure l, but pro e th li ht d f ren unde e d.me This. underfeed'mechanisrn consists of a housing 15, capable ofrotating about a vertical axis, in which housing there are two.cylinders 1 1;'. The housing is rotatable. on the ball; bearings v 1Qby. means of a worm gear 17. u

In the cylinders 11 there are plungers 10 which can e m v d up anddqw hyrau ic a draulicranrs 9 are actuatedby an oil pump 18, located in thecenter of ,-th e .housing 1-5. The underfeed device is so mounted that,when one cylinder 11' is under the bunkerchamber 19, the other. cylinder11 is under the delivery conduit 7 The operation of this underfeeddeviceis as follows:

Lime frorn bunker 8g is fed along conduit 8 by means of: a worm 3 intobunitcr 19, From bunker 19, the material drops into theone cylinder 11.The plunger liii appertaining tothis cylinder is then in its lowermostposition, while'the. plunger T0, of the cylinder located under theconduit 7 has just. pushed a charge of lime from thatcylinder. into, theconduit]. Subsequently, the housing is turned so that the full cylinderispositioned under conduit 7;; and; the. empty cylinder. is positionedunder bunker 19, after which theone cylinder is filled and the otheremptied.

in order. to prevent leakage of gases from the, furnace through conduit7 to the outside, the housing 15 is surrounded by a water. seal2i).

Through the pipes 7a, hot gases for the preheating of the lime charge,can. be supplied. If desired, this. pre: heating may take place, if thelime charge is mixed with a li-ttle fuel, by combustion of; thefuel withair or oxygen supplied through the pipes, 7 1. To keep the required feedpressure in theconduit pipe-7 relatively low, a lubricant (e. g] l /z%graphite) preferably, is added to the charge in, bunker 8a.

Example Using the furnace and underfeedingdeviceof Figure 1, there werefed every hour 350kg. of calcium oxide containing 100. kg. of cokeand3.5 kg. of graphite from bunker 8a; 1580 kg. of coke through fillinglock la, 900 kilolite rs. of oxygen (standard temperature and pressure)through tuy eres 3, Q kiloliters ofcarbon dioxide (standard temperatureand pressure) through blast openings 4 and 500 kiloliters of air(standard temperature and pressure) through feed pipes 7a.

We claim:

1. A furnace. suitable for preparing calcium carbide from a solid,highly carbonaceous fuel and a calcium oxide containing materialcomprising a hearth provided with a plurality of tuyeres, at least onefeed opening for solid fuel near the top of the furnace above saidtuyeres,

at least one gas discharge opening near the top of the furnace abovesaid tuyeres, a feed opening at a point below The hy-.

calcium oxide containing material into the reaction zone.

4 the ring of tuyeres andmeans for feeding a supply ofsolid of thefurnace through said lower feed opening, said furnace being adapted toproduce calcium carbide while avoiding considerable vaporization of limecomponents and thereby avoiding difliculties due to blocking andbridging of the charge in the upper portion of the fuel bed.

2. A furnace according to claim 1, including a tap hole below the ringof tuyeres for removal of carbide product and whereinthe means forsupplying calcium oxide material into the reaction zone comprises aconduit leading to said feed opening, supply means for the calcium oxidecontaining material and feeding means for transferring said calcinmoxide. from said supply means to said conduit, saidfeedingmeanscomprising plunger means, said plunger means reciprocating between saidsupply means and said conduit.

3. A, furnace according to claim- 2, wherein communicating with,saidiconduittleading to said feed opening there-are gas,supplyingmeansand .wherein said plunger supply means and; said; plunger;being. in extended position when it deliverscalciumoxide to saidconduit..

4. A furnace according.to, claim.3, .wherein said cylinder ispivQiabletabout a, horizontal ,axis.

5. A furnace according to claim 1, including a tap hole .belowthe ringofittuyeres for. removal of carbide product;- and whe cm the means-for.supplying calcium oxide rnaterial intqfihe reaction; zone; comprises a.conduit leading to said feed;open ng,,supplyv means. for the,-

calcium: oxide containing'material and. feeding, means fortransferringsaid calcium oxide; from said supply means.

to said conduit, said feeding means comprising a pair of t p t ngtp n eeans, aidp r means recipro cating between saidsupply means and saidconduit.

6. A furnace according to claim 5, wherein communicating withsaidfconduit leading to said feed opening there are gassupplyingmeansand .wherein each of said plunger; means isguided, by a cylinder, one ofsaid plunger means being in-recessedposition;andin position to receivecalciumoxidefrom thecalcium oxide supplying means when the other of saidplunger means is in extended positicn and in positionto deliyercalciumoxide to said duit..

7. The furnace of-claim 6, wherein said cylinders and pair ofplungermeans are housed in a housing, said housing being rotatable about avertical axis.

References Cited in the file of this patent UNITED STATES PATENTS

1. A FURNACE SUITABLE FOR PREPARING CALCIUM CARBIDE FROM A SOLID, HIGHLYCARBONACEOUS FUEL AND A CALCIUM OXIDE CONTAINING MATERIAL COMPRISING AHEARTH PROVIDED WITH A PLURALITY OF TUYERES, AT LEAST ONE FEED OPENINGFOR SOLID FUEL NEAR THE TOP OF THE FURNACE ABOVE SAID TUYERES, AT LEASTONE GAS DISCHARGE OPENING NEAR THE TOP OF THE FURNACE ABOVE SAIDTUYERES, A FEED OPENING AT A POINT BELOW THE RING OF TUYERES, A FEEDOPENING AT A POINT BELOW CALCIUM OXIDE CONTAINING MATERIAL INTO THEREACTION ZONE OF THE FURNACE THROUGH SAID LOWER FEED OPENING, SAIDFURNACE BEING ADAPTED TO PRODUCE CALCIUM CARBIDE WHILE AVOIDINGCONSIDERABLE VAPORIZATION OF LIME COMPONENTS AND THEREBY AVOIDING DUE TOBLOCKING AND